text: Isotropic deviation, in EMF measurements, is a parameter that describes the accuracy in measuring field intensities irrespective of the probe's orientation.
  If the field is obtained by three measurements in an orthogonal X, Y, Z configuration in the form:
  a sufficient condition for the expression to be true for every three orthogonal coordinates (X,Y,Z) is for the probe radiation pattern to be as close as possible to ideal short dipole pattern, called sin θ:
  where A is function of frequency.
  The difference between ideal dipole radiation pattern and real probe pattern is called isotropic deviation.